The objective of this project is to identify and quantitate the effects of risk factors in the environment in transformable mammalian cells in culture. Since the biological effects of xenobiotics found in the environment including chemical carcinogens depend on their metabolic activation and detoxification, and on their accessibility to the target cells, this proposal will provide information dealing not only with procarcinogens which may be metabolized to ultimate carcinogens (primary risk factors), but also with agents that have co-carcinogenic potential (secondary risk factors) due to their ability to modify the enzyme activities concerned with activation and deactivation of the procarcinogen. The studies are conducted in the C3H 10T1/2 CL8 cells using benzo(a)pyrene and 3-methylcholanthrene as primary risk factors. A number of insecticides and other environmental agents are also studied for their roles as primary and secondary risk factors.